John Crane Sealing Tech: Cutting Water Use in Copper Mining

John Crane has retrofitted a mechanical seal on an underflow thickener slurry pump at an active copper mine. The company claims it cuts clean water needed for sealing by around 288,000 litres a day.

If accurate, the results have promising wider implications for the copper mining industry, which operates in water-scarce areas and is under pressure to reduce its water footprint.

The retrofit also promises to reduce the operational downtime incurred while replacing the pump's shaft sleeve. Replacements were previously performed every four months and each required a full mechanical crew working across 36 hours, as well as a 100-tonne crane.

Copper mining is heavily concentrated in some of the world's most water-stressed regions, including the Atacama Desert in Chile, Zambia and the Democratic Republic of Congo. 

Water is essential to copper ore processing. With supplies running low, the industry is under increasing scrutiny from regulators and local communities. 

A copper mining operation can potentially run dozens of pumps like the one John Crane has retrofitted, making the water saving potential substantial.

Why water matters in copper mining

Water is used at almost every stage of copper ore processing, from grinding and flotation through to tailings management. As a result, a large copper operation can consume millions of litres a day.

The problem is that the regions where copper is most abundant are often the same regions where water is most scarce. The Atacama Desert in Chile hosts some of the world's largest copper mines, yet the region receives an average of less than 1 millimetre of rain per year. 

Zambia and the Democratic Republic of Congo also face serious water management challenges, and today we are seeing mining operations competing for resources with local communities and agriculture.

In reaction, regulators in these regions are tightening water use requirements for industrial operators. Investors today are asking harder questions about the operational and geopolitical risks of mining in these regions. As our recent coverage of Barrick's proposed restructuring shows, scrutiny of African mining operations is intensifying across multiple fronts.

The pressure on copper miners to reduce consumption is intensifying, and the industry is looking hard at where reductions can be made.

How John Crane’s retrofit works

The underflow thickener pump is one of the most demanding applications in a copper mine's processing circuit. It moves dense slurry, in this case running at around 65% solids, from the bottom of the thickener into the tailings transport system. 

If it stops working, processing backs up fast and it can cause significant downtime.

The pump previously used a traditional packing arrangement, which was essentially compressed rings of fibrous material packed around the shaft to prevent leakage. 

In abrasive slurry service, packing wears quickly and requires a constant flow of clean water to flush solids away from the sealing point and keep it cool.

John Crane replaced the packing with a mechanical seal, made of two precision-machined faces pressed together to form a near-zero leakage barrier. One face rotates with the shaft while the other is stationary. 

The package was designed to retrofit without modifications to the pump itself, with an adapter sleeve fitted to suit the shaft.

To handle the hostile operating environment, the seal uses a controlled flush arrangement to maintain a clean fluid environment at the seal faces. Diamond-faced materials provide additional robustness in the event that flush pressure drops and solids enter the seal chamber.

At 270mm in shaft diameter, it is the largest slurry seal John Crane has sold to date, the company says.

The results 

According to John Crane, the sealed pump is using around 7.5 to eight cubic metres of water per hour for sealing. A pump on the same site which is running the traditional packing is consuming around 20 cubic metres per hour. 

That gap works out at roughly 12 cubic metres per hour, which equates to approximately 288,000 litres of clean water saved every day.

The retrofit also reduces mine maintenance and operational downtime. The new seal is designed to only need replacing during the site's annual major service interval, which is when the impeller and liners are replaced. 

Previously, the shaft sleeve needed replacing every four months, each time requiring a full mechanical crew, a 100-tonne crane and around 36 hours of work across two shifts.

Warren Smith, Global Mining Market Director at John Crane, says the project demonstrates what improved sealing could deliver. "Underflow thickener pumps are among the most critical assets in a mine's tailings circuit, so customers are understandably cautious about change," Smith says. 

"This project is a practical example of how improved sealing can reduce maintenance exposure and cut the clean water required for sealing, while supporting more predictable planned maintenance."

What it means for mining

The results from a single pump retrofit are promising, and the opportunity for widespread water use reductions is clear when you consider the scale of a copper operation. A large mine can run dozens of pumps handling abrasive slurry across its processing circuit, many of which are likely still running traditional packing arrangements.

Applying the same retrofit across a fleet of pumps at a single operation could deliver water savings running into millions of litres a day. 

In regions like the Atacama, Zambia and the Democratic Republic of Congo, where water supplies are finite and under pressure, that level of reduction could have a big impact on both operational costs and regulatory compliance. 

John Crane is a division of Smiths Group, a FTSE 100 industrial technology company with operations across more than 50 countries. Its global footprint means the technology demonstrated at this copper mine could be deployed across multiple jurisdictions and operating environments.

The retrofit does not solve mining's water problem, but it suggests that a meaningful part of the solution might be found in operational upgrades rather than headline-grabbing sustainability commitments.